Fiber-optic communication systems have been used extensively in many areas, such as, telecommunication transmission, data transmission, CATV and video transmission and distribution. More recently, wavelength division multiplexed (WDM) systems have become more important as a result of their ability to utilize the significant bandwidth of single mode fiber cables.
A WDM communication system has the ability to provide two or more communications channels over a common optical fiber, where the two or more communications channels are differentiated by optical wavelength. The use of WDM systems has recently become more prevalent in the telecommunications industry due to the escalation of bandwidth requirements for many telecommunications applications. One integral part of a WDM system is that part of an electro-optical transmitter which includes a light producing source and a modulation mechanism for the light source by which the light produced therefrom is translated or modulated into meaningful bit streams of information. Well-known transmitter devices for use in fiber optic communications systems have included LED-type transmitters as well as the more commonly used laser transmitter. One particularly advantageous device for producing modulating light signals for use in a WDM fiber optic system is termed an Electro-Absorption-Isolated-Laser-Module (EMILM).
An important parameter which characterizes the (spectral) performance of such an EMILM device in a WDM system is the dynamic wavelength movement or chirp that the device can achieve. This dynamic wavelength movement parameter is generally measured in Angstroms, where the chirp parameter produced by an ideally functioning EMILM device would be zero, i.e., no wavelength movement produced by the device.
These EMILM devices for use in WDM systems are typically packaged in industry standard housings, for example, butterfly metal packages with ceramic (dielectric) electrical feedthrus. The electrical feedthrus when combined with the body of the package will many times constitute a path whereby the electrical drive signal provided to the EMILM device becomes distorted from its originally intended shape. This distortion is undesirable as it tends to make the WDM communications signal and the channel in general less reliable, as well as negatively impacting the chirp parameter. Accordingly, there is a need for an EMILM-type-communications device which reduces the distortion of the electrical drive signal to the electro-optical device, hence producing a lower chirp.